Increased Cyclin G1 Immunoreactivity During Alzheimer's Disease

Numerous proteins are alternatively expressed in neurons and glia during Alzheimer's disease (AD) and may contribute to the regulation of neuronal cell death or function in regenerative responses to neuronal injury. A recently described member of the cyclin gene family, cyclin G1, is expressed in post-mitotic neurons in the adult rat brain and is expressed at high levels after brain injury. In the current study we examined the expression and subcellular distribution of cyclin G1 in non-demented adult and AD brain. While low levels of cyclin G1 protein were observed in pyramidal neurons in control brain, abundant cyclin G1 immunoreactivity was present in the cytoplasm of pyramidal neurons in the neocortex and hippocampus of AD brain. Cyclin G1 immunoreactivity was not present in cells containing neurofibrillary pathology. Our results indicate that cyclin G1 is expressed in human adult brain and exhibits increased immunoreactivity in the cytoplasm of pyramidal neurons in AD. In addition, cyclin G1 immunoreactivity was not evident in cells containing cytoskeletal pathology.